rotate 180 degress on z axis smoothly

I’m trying to rotate my ball 180 degrees on the z axis, I have tried transform.rotate, but it looks like it instantaneously changes, I want to make it visually rotate instead of instantly rotate it. Anyone?

Vector3 rotator;
float around;

void Update()
{
around += Time.deltaTime;
rotator = new Vector3(0f,0f, Mathf.Clamp(180, 0, around)));
ball.transform.rotation = rotator;
}

Didnt have time to test.You can control the speed by dividing or multiplying the Time.deltaTime